1. Field of Invention
The present invention relates to a coupled torsion beam axle type suspension system, and more particularly, to a coupled torsion beam axle type suspension system for controlling movement (e.g., toe) characteristics thereof with respect to a side force, when a vehicle turns.
2. Description of Related Art
Generally, despite a limitation in design performance factors such as ride comfort, driving stability, etc., a coupled torsion beam axle type suspension system (hereinafter referred to as a CTBA) has been primarily applied to rear wheel suspension systems for compact and mid-size cars, compared with independent-type suspension systems, because they have advantages of light weight and low production cost due to their simpler components.
FIG. 1 is a perspective view of a CTBA according to one example of the related art. Referring to FIG. 1, the CTBA according to one example of the related art is provided with a torsion beam 1 in a width direction of a vehicle, trailing arms 5 respectively coupled to opposite ends of the torsion beam 1, and carriers 3 for mounting wheel tires at the trailing arms 5. A spring seat 9 for mounting a spring 7 thereon and a shock absorber pin 13 for coupling with a shock absorber 11 are provided at a rear inner portion of the trailing arm 5.
In addition, a vehicle body-engaging unit 15 is provided at a front end portion of the trailing arm 5 to be coupled to a vehicle body. Each vehicle body-engaging unit 15 includes a trailing arm bush 21 that is coupled to the front end portion of the trailing arm 5, and a mounting bracket 23 that is coupled to the trailing arm bush 21 through a bolt 25.
According to the CTBA having the aforementioned configuration, wheels are deformed due to twisting deformation characteristics of the torsion beam 1, and in addition to that, positions of the trailing arm 5 and a configuration of the vehicle body-engaging unit 15 cause deformation of the wheels.
The vehicle should maintain an under-steering tendency in consideration of driving stability when it turns, and for this purpose, it is ideal that a rear outer wheel of a turning vehicle (hereinafter referred to as a rear outer wheel) should be induced to toe-in and a rear inner wheel of the turning vehicle (hereinafter referred to as a rear inner wheel) should be induced to toe-out.
However, the entire CTBA rotates by the deformation of the trailing arm bush 21 and generates a toe angle at the rear outer wheel. That is, when the vehicle turns, the bumped rear outer wheel is applied with the side force and thus is likely to be induced to toe-out, while the rebounded rear inner wheel is applied with the side force and thus is likely to maintain the previous toe angle or to be induced to toe-in, such that the vehicle is over-steered in general and thus causes deterioration of turning stability.
As a mechanical instantaneous rotational center point of the CTBA with respect to the vehicle body (i.e., an intersection of lines that extend in engaging directions of the trailing arm bushes 21 engaged to the vehicle body) is positioned in front of the wheel centers, the rear outer wheel has a tendency to toe-out due to the side force while the rear inner wheel has a tendency to toe-in due to the side force.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.